Next comes a pilot hole using a 1/4 inch titanium coated drill bit with a pilot bit on the end for drilling in metal: (sorry for the blurry pic)
And next are the 1/4 inch pilot holes. I used some boe-lube to lubricate the bit ocassionally:
The process of drilling all these holes took me a while. It seemed that in some cases the bits would dull after the first use and would not cut as well for subsequent holes, and other times....well, lets just say I found a way to break "titanium" with relative ease a few times! Notice the slight bend in one of the bits in the following pic. This was a 7/32 bit - slightly smaller than the 1/4 inch bit, but apparently a whole lot less rigid. I found that there is a technique involved where as the drill but starts to get close to exiting out the other side, you need to ease off the pressure being applied on the bit. That seemed to help some.
It seems that when the bit starts to penetrate the far side of the metal, it tends to grab quite hard - probably due to my 3/8 inch electric drill not having enough RPM to do this correctly - and the keyless chuck that kept coming loose every so often did not help much either. Fortunately the 1/2 inch drill bit never faltered on me, so those holes all went fairly well:
And finally, I am going to use Red Head 2 1/4 inch x 3/8 inch concrete anchors to secure each wing stand to the concrete. My plan is to use a rotary hammer drill with a 3/8 inch carbide bit, place and draw the outline of the angles and the mounting holes with a sharpee, and got to town with the hammer drill. These anchors require a minimum depth of 1 1/2 inches, and the instructions say to drill another 1/4 inch deeper - so 1 3/4 inches deep is all that is needed. After you account for the 1/4 inch depth of the angle and the washer and nut, it leaves about 1/8 of an inch to torque down the nut to secure the stands to the anchors.
No, this is not going to be the final resting place of this wing stand, right over one of many cracks in my floor! I just took this to show the alignment of the holes in the flanges after they are drilled to size. I did trial fit one of the 3/8 inch anchors into the 1/2 inch hole, and I have to agree with Aaron that having a bit of wiggle room for the bolt is a good idea. The washer and nut feels like it will securely attach the stand to the floor, and I am not concerned about the over-sized mounting holes for the bolts I am using. These suckers are extremely heavy, so positioning and marking the locations for the stands on the floor will be a 2 person job. The last thing I want is for one of these things toppling over on me - that would be a very bad day in the airplane shop indeed.
One more step done......
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